So WMW has a subscriber only thread titled Expert Claims to Have Beaten Google Sandbox. The best info is in the free Matt Cutts on the Google Sandbox thread. DaveN mentions a site that was quickly out of the box. His main tip?

don't think like an SEO
build site go get links from ......

Dave also showed some encrypted logfiles showing that he was getting decent traffic from a couple sites outside of search engines.

My guess is the ability to seperate out searches from Google Search (When users search for my keywords on Google) and the Search Network (When users search for my keywords on Google's search partners).